feat(tactical-app): full sovereign military suite in Flutter with first-run onboarding, artillery ballistics, HLZ assessment, minefield breach, isochrone, symbols, and overlays

packages/tactical_app/lib/widgets/tactical_viewshed_sheet.dart

@@ -31,7 +31,7 @@ class _TacticalViewshedSheetState extends State<TacticalViewshedSheet> with Sing
   late LatLng _currentObs;
   double _radiusKm = 5.0;
   double _observerHeightM = 2.0;
-  int _rayCount = 360; // 360 continuous 1-degree radial rays (15-20ms)
+  final int _rayCount = 360; // 360 continuous 1-degree radial rays (15-20ms)
   Viewshed360Report? _report;
   bool _isCalculating = false;
   bool _showCoordInputs = false;
@@ -170,7 +170,13 @@ class _TacticalViewshedSheetState extends State<TacticalViewshedSheet> with Sing
                       borderRadius: BorderRadius.circular(10),
                       border: Border.all(color: const Color(0xFF22C55E)),
                     ),
-                    child: const Icon(Icons.radar, color: Color(0xFF4ADE80), size: 22),
+                    child: _isCalculating
+                        ? const SizedBox(
+                            width: 22,
+                            height: 22,
+                            child: CircularProgressIndicator(strokeWidth: 2, color: Color(0xFF4ADE80)),
+                          )
+                        : const Icon(Icons.radar, color: Color(0xFF4ADE80), size: 22),
                   ),
                   const SizedBox(width: 12),
                   Expanded(